Bloomberg is shaking up its trading arm

Ray Tierney, the global head of Bloomberg's broker-dealer and sell-side trading solutions business, has left the firm, according to people familiar with the matter.

Tierney was previously CEO of Bloomberg's agency brokerage, called Tradebook. Glenn Lesko, who replaced Tierney in that role two years ago, has also left the firm, according to people familiar with the matter. His departure was first reported by Financial News.

Bloomberg is a one-stop shop for Wall Street traders, aggregating reams of data used to make investing decisions, covering news that moves financial markets, and — through Tradebook — giving customers a way to execute trades.

"But we feel we have stability by being part of Bloomberg and have been focused on developing better connectivity to the rest of the company's products to provide clients with a better product experience," he added.

Bloomberg remains committed to the business, and a successor to Tierney will be announced shortly, according to one person familiar with the matter.

The changes at Tradebook come as Bloomberg's core client-base, the financial sector it serves shrinks. Earlier this week, industry consultant Burton-Taylor said that Bloomberg terminal counts shrank in 2016 for only the second time in company history.

Still, Bloomberg accounted for 33.4% of the market for market data, analysis and news, posting growth in its data feed and other non-terminal businesses.